Somatostatin (SRIF) is a diffusely localized neuropeptide with multiple regulatory actions in both the central nervous system (CNS) and the gastrointestinal (GI) tract. In addition to multiple immunoreactive forms of SRIF, there are other SRIF prohormone related peptides generated by a relatively complex process of proteolytic cleavages. The pathophysiological role of SRIF and related peptides in degenerative CNS diseases, GI disorders, and diabetes mellitus in man is emerging. SRIF also offers therapeutic promise in the treatment of peptic ulcer disease, pancreatitis, and insulin dependent diabetes. The long range objectives of this project are to define the post-translational processing of the SRIF prohormone and its intermediate peptide fragments to their final biologically active and inactive products, to define the tissue specificity of the processing of prosomatostatin, and to characterize the phenotypical effects of the integration and expression of the metallothionein-SRIF (MI-SRIF) fusion gene in mice. These studies will have important implications on the factors controlling neuropeptide synthesis and the potential usefulness of genes encoding polypeptide hormone precursors in gene therapy. Three biological models of SRIF production will be studied; the tuberoinfundibular tract of the rat hypothalamus and median eminence, a cell culture line of baby hamster kidney (BHK) cells transfected with the MT-SRIF gene, and transgenic mice that developed from eggs microinjected with the MT-SRIF gene. Specific aims are to: 1. Purify radiolabeled peptides generated from the SRIF prohormone by tuberoinfundibular neurons and BHK cells and determine the amino acid sequences and cleavage sites of the peptides by automated Edman degradation and micro-sequencing. 2. Determine the immediate molecular precursor to the 1.6 K immunoreactive SRIF peptide generated in BHK cells by pulse-chase radiolabeling experiments. 3. Characterize the tissue specific expression of the MT-SRIF fusion gene in transgenic mice by Northern blot hybridization of extracted mRNA and radioimmunoassay of peptides. 4. Identify the biological effects of sustained production of SRIF related peptides in transgenic mice by a detailed examination of their growth, neurological development, anatomical changes in organs, and hormonal responses to standard dynamic endocrine testing.